AP65251

Document number: DS36109 Rev. 1 - 2

2 of 19

www.diodes.com

October 2017

© Diodes Incorporated

AP65251

Pin Descriptions

Pin

Name

Pin Number

Function

TSOT26

BST

1

High-Side Gate Drive Boost Input. BST supplies the drive for the high-side N-Channel MOSFET a 0.01µF or

greater capacitor from SW to BST to power the high side switch.

GND

2

Power Ground.

FB

3

Feedback sensing terminal for the output voltage. Connect this pin to the resistive divider of the output. See

Setting the Output Voltage.

EN

4

Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on the regulator; low to

turn it off. Attach to IN with a 100kΩ pull up resistor for automatic startup.

VIN

5

Power Input. VIN supplies the power to the IC, as well as the step-down converter switches. Drive VIN with a

4.5V to 16V power source. Bypass VIN to GND with a suitably large capacitor to eliminate noise on the input to

the IC. See Input Capacitor.

SW

6

Power Switching Output. SW is the switching node that supplies power to the output. Connect the output LC

filter from SW to the output load. Note that a capacitor is required from SW to BST to power the high-side

switch.

Functional Block Diagram

5

VIN

4

EN

6

SW

3

FB

2

GND

Internal

Reference

-

+

+

Digital Control

Logic

1

BST

Ref

5V

SS

OCP

Soft Start

Min Off

Time

S

R

Q

+

Se

On Time

Compute

VIN

Q

One Shot

SW

Frequency

Lock Loop

0.6V

Vcc

Regulator

SS

SW

UVLO

Logic

Control

5V

Figure 2. Functional Block Diagram